Field of the Invention
The present disclosure relates to a method of manufacturing a flexible device, the flexible device, a solar cell, and a light emitting device, and more particularly, to a flexible device manufacturing method through which various large area devices having flexible properties are precisely aligned with each other and a flexible device having greater economic feasibility is manufactured, the flexible device, a solar cell, and a light emitting device.
Description of the Related Art
As ubiquitous as the information age has become, the demand of a flexible device conveniently usable in various living conditions is being increased. Thus, research for realizing a flexible device is being conducted in many different fields. Among these is research using nano materials such as a nano wire (NW) and a carbon nano tube (CNT) or using organic semiconductors is in the spotlight. In 2001, the world's first flexible display using an organic semiconductor was realized by Bell Labs. Since the materials have low electrical performance (effective mobility of the organic semiconductor and the nano wire are about ˜1 Cm{circumflex over ( )}2/Vs and about ˜5 Cm{circumflex over ( )}2/Vs, respectively) and it is difficult to secure uniformity of the material and perform processes, it has been very difficult so far to commercialize the flexible display using the organic semiconductor. To solve these limitations, a printable microstructure semiconductor (μs-Sc) was introduced at the Illinois Institute of Technology in 2004 (Appl. Phys. Lett. 84, 5398, 2004).
This technology in which single crystal silicon having superior device performance directly takes off from a bulk silicon substrate to obtain a microstructure semiconductor. The obtained microstructure semiconductor is then transferred onto a flexible substrate using a soft lithography process. The device manufactured by transferring the single crystal microstructure semiconductor onto the flexible substrate has the most excellent electrical performance (effective mobility>about 500 Cm{circumflex over ( )}2/Vs) among existing flexible electronic materials (IEEE Electron Device Lett. 27, 460, 2006).
According to this technology, the microstructure semiconductor is designed in a dumbbell shape, and a lower portion of the microstructure semiconductor is etched to manufacture a support shaft. The microstructure semiconductor then takes off using a polydimethylsiloxane (PDMS) stamp to selectively transfer only the microstructure semiconductor disposed on a desired position.
According to this technology, a device may be manufactured on a desired position of a plastic substrate using the selective transfer, as well as the microstructure semiconductor remaining on an SOI substrate after transferring may be transferred onto a position required later to use the microstructure semiconductor. As a result, the manufacturing costs may be reduced.
When the microstructure semiconductor is selectively transferred, because the PDMS stamp having an uneven shape is used, a sagging effect in which a recessed portion is collapsed due to proper properties of the PDMS may occur to separate the undesired microstructure semiconductor. In addition, when the microstructure semiconductor is transferred, contraction and relaxation of the PDMS may occur. As a result, it is difficult to precisely align the microstructure semiconductor with the PDMS stamp on the silicon substrate.
Furthermore, it is difficult to etch a device having a relatively large area due to a limitation of an infiltration rate of an etchant and the sagging effect. When the silicon substrate is etched downward from a top surface, a limitation of a unit device may be about 100 μm. Thus, in the method of manufacturing the flexible device according to the related-art, there is a limitation to the manufacture of large area flexible devices such as solar cells and light emitting devices. There is an urgent need for technologies which can overcome the above-described limitations.
The solar cells may be expected as an item capable of applying the flexible device. The solar cells convert solar energy into electricity energy. Also, the solar cells are called an electronic device, which generates electricity using two kinds of semiconductors referred to as a P-type semiconductor and an N-type semiconductor. Typically, a silicon substrate solar cell having about 25% of efficiency makes up the main part of the solar cells. However, solar cells formed of various materials, which can realize high efficiency are being developed in recent years.
InGaN among such materials has an emission wavelength covering the range from an approximately UV wavelength region to a green spectrum region and is widely used as an active material of a related-art light emitting device or laser diode. Recently, since InGaN has a band gap adjustable in the entire alloy region and has high carrier mobility, drift velocity, radiation resistance, and characteristic having a light absorption index of about 105 cm-1 that is about a band boundary, InGaN is being in the spotlight as a new material for solar cells.
However, an InGaN-based solar cell reported so far is rigid like silicon or sapphire and has a structure in which a rigid substrate includes an InGaN layer. Thus, an InGaN-based solar cell formed on a flexible substrate is not yet disclosed. Particularly, an intense process of manufacturing solar cells based on a high-temperature semiconductor process limits a range of substrate selection.